The much dreaded Agent Orange defoliated vast tracts of forested land in Vietnam, as part of the US military's warfare programme, killing or maiming 400,000 people and causing birth defects in half a million children, say researchers.
But even if all the dioxin, an extremely toxic compound in Agent Orange, were eliminated from the planet, researchers say it would continue to wreck the health of the descendants of those exposed to it half a century ago.
Biologist Michael Skinner from Washington State University and members of his lab say dioxin administered to pregnant rats resulted in a variety of reproductive problems and disease in subsequent generations, the journal Public Library of Science ONE reported.
The first generation of rats had prostate disease, polycystic ovarian disease and fewer ovarian follicles, the structures that contain eggs.
To Skinner's and colleagues' surprise, the third generation had even more dramatic incidences of ovarian disease and, in males, kidney disease, according to a Washington statement.
"Therefore, it is not just the individuals exposed, but potentially the great-grandchildren that may experience increased adult-onset disease susceptibility," said Skinner.
Skinner is a professor of reproductive biology and environmental epigenetics - the process in which environmental factors affect how genes are turned on and off in the offspring of an exposed animal, even though its DNA sequences remain unchanged.
In this year alone, Skinner and colleagues have published studies finding epigenetic diseases promoted by jet fuel and other hydrocarbon mixtures, plastics, pesticides and fungicides, as well as dioxin.